"In order to answer the question about the conditions under which sex is morally wrong, we need to know what it means to consent to sex. “Consent” is shorthand for “voluntary informed consent.” Agreeing to have sex does not count as consenting to an entire sexual encounter for three reasons. 1. Consent given prior to a sexual encounter can be withdrawn at any time. 2. Agreeing to have sex can be involuntary. Submission to a sexual encounter is involuntary when it is forced upon a dissenting person by the use of physical force, threat or incapacitating behavior. It is admittedly difficult to specify what exactly counts as threatening or incapacitating behavior. A dissenting person who is too shocked by the other person’s sexual approach to move away or resist is incapacitated, even if she does not feel threatened. 3. The person may not be in a position to consent. Children, for example, are unable to consent to sex. This is not because minors are unable to consent to anything. Certainly, if a parent asks an average six-year old whether she would like the parent to brush her hair, and the six-year old responds that she does, her agreement counts as consent. Six-year olds are normally old enough to understand what it means for someone to brush their hair, and hair brushing does not ordinarily have unforeseen and potentially harmful consequences. So, not only is the child voluntarily entering into the interaction, she also understands the nature and consequences of the action. A six-year old cannot ordinarily consent to sex, however, as she is not in a position to understand what the act entails. Similar remarks apply to at least some mentally challenged individuals."